Oulu-NPU [1]} has four challenging protocols, which evaluate the model robustness against the unseen environment, unseen spoof mediums, unseen capture devices, and all of the above, respectively. The number of classes during training are 5, 3, 5, and 3, respectively. As shown in Tab. REF , our simple patch-based recognition approach achieves the best performance in all protocols. It clearly verifies the better generalization ability of the features learned through the patch recognition proxy tasks.
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